The present invention relates generally to acoustical insulation materials and, more particularly, to acoustical insulation materials utilized within vehicles.
It is generally considered desirable to reduce noises generated from appliances, and from within buildings, vehicles, and the like. With respect to vehicles, road noise, tire noise, engine noise, vehicle vibrations, etc., may pass through a vehicle body and into the passenger compartment.
It is generally considered desirable to reduce the level of noise within a vehicle passenger compartment. Noises, such as road noise, engine noise, vibrations, etc., may be attenuated through the use of various acoustically absorptive (or reflective) materials. For example, sound attenuating materials are conventionally provided in conjunction with carpeting, door panels, and headliners.
Various sound attenuating materials have been developed for use in reducing noise levels within passenger compartments of vehicles. For example, U.S. Pat. No. 4,851,283 to Holtrop et al., proposes a thermoformable laminate for use in headliners. The headliner comprises a non-woven fabric bonded to a foamed polymer sheet. The fabric is formed from a blend of low melting staple fibers and high melting staple fibers.
U.S. Pat. No. 5,298,694 to Thompson proposes a non-woven acoustical insulation web. The web comprises thermoplastic fibers, and particularly a blend of melt-blown microfibers and crimped bulking fibers.
U.S. Pat. No. 5,677,027 to Masuda et al., proposes a sound insulating structure comprising a covering layer, a panel, and a cushioning layer. The cushioning layer comprises a first fiber such as polyethylene terephthalate (PET) and a second fiber that is of a shell-core construction wherein the majority of the core is PET.
U.S. Pat. No. 5,817,408 to Orimo et al., proposes a sound insulating structure which includes low and high density thermoplastic fibers. PET is preferred as a thermoplastic synthetic fiber.
U.S. Pat. No. 4,529,639 to Peoples, Jr. et al. proposes a molded foam-backed carpet assembly which includes a carpet layer, a moldable thermoplastic polymer layer and one or more foam pads fusibly bonded to the thermoplastic layer and extending over less than the entire surface of the thermoplastic polymer layer to provide desired cushioning and sound and thermal insulation only in preselected areas of the carpet.
In general, the ability of conventional materials to attenuate sound increases as the amount of material increases. Unfortunately, increased materials often increases the weight of sound attenuating material, which may be undesirable. Accordingly, there is a continuing need for acoustical insulation materials that exhibit superior sound attenuating properties, while also being lightweight and low in cost.
In view of the above discussion, sound attenuating laminates, and methods of making the same, are provided. According to an embodiment of the present invention, a surface of a non-woven (or woven), fibrous layer of material (e.g., containing thermoplastic or thermosetting fibers) is heated to form a stratum of melted fibers having a density different (i.e., greater) than that of the remainder of the fibrous layer. The density of the melted fibers is effective in attenuating noise traversing the fibrous layer of material. Upholstery material (preferably heated), such as carpeting, is attached to a surface (either adjacent to or opposite from stratum of melted fibers) of the heated fibrous layer. The fibrous layer and upholstery material is then subjected to compressive molding pressure to obtain a desired shape. The compressive molding pressure may further tune the sound attenuating properties of the fibrous layer by selectively changing the densities of one or more portions of the fibrous layer.
According to other embodiments of the present invention, a surface of a first non-woven (or woven), fibrous layer of material is heated such that fibers adjacent the surface form a stratum of melted fibers that has a density greater than a density of the remainder of the fibrous layer. The density of the stratum is effective to attenuate noise traversing the first fibrous layer of material. Upholstery material, such as carpeting, is attached to a surface (either adjacent to or opposite from stratum of melted fibers) of the heated first fibrous layer. The first fibrous layer and upholstery material are then subjected to compressive molding pressure (preferably in the presence of heat) to obtain a desired shape. The compressive molding pressure may further tune the sound attenuating properties of the first fibrous layer by selectively changing the densities of portions of the fibrous layer. A second non-woven (preferably heated), fibrous layer of material is attached to an opposite surface of the first fibrous layer. The first and second fibrous layers and upholstery material are then subjected to compressive molding pressure (preferably in the presence of heat). The compressive molding pressure may further tune the sound attenuating properties of the combined first and second fibrous layers by selectively changing the densities of portions of the first and second fibrous layers.
By controlling and differentially molding and/or melting fibers through temperature and pressure variation, laminates according to embodiments of the present invention can be xe2x80x9ctunedxe2x80x9d to provide desired sound deadening and absorption properties in selected locations. The term xe2x80x9ctunedxe2x80x9d means that portions of laminates can be formed to have a specific acoustic impedance designed to attenuate sound in one or more frequencies or frequency bands. Moreover, laminates according to embodiments of the present invention may have reduced overall weight compared with conventional sound proofing materials, and without sacrificing sound attenuation properties.